The present invention relates to novel thin layers for microsystem techniques and microstructuring which may be employed within the range of such technologies in various manners.
The thin layers heretofore employed according to the state of art in the microsystem technique and in microstructuring, as for example for manufacturing membranes, sandwiched system contacts and circuits are based on the use of inorganic layers, such as layers of SiO2, Si3N4, and Al2O3 frequently employed, and metal layers and metal layer systems, respectively. Poisonous chemicals and such being harmful to health, as for example strong acids, alkalies, and oxidants, are employed to produce the desired structures, or extremely expensive processes, such as reactive ion etching and plasma etching, respectively, are required therefor (refer to S. Bxc3xcittgenbach, Mikromechanik, B. G. Teubner, Stuttgart, 1994). The only organic layers which are to be used in structuring processes are photoresists which after the desired structure being imparted to the layer to be structurized are removed, as a rule.
It is an object of the present invention to provide thin layers which can be manufactured less critically and more economically than previous conventional thin layers under use of existing technologies in microstructuring and which are suited in a particularly advantageous manner for setting-up substance libraries.
The object is realized by the characteristic features of the first claim.
Advantageous embodiments are covered by the succeeding claims. It was found that in the field of microstructuring the masking layers capable of structurizing and employed previously to this end, such as photoresist layers, may locally affect the properties of biopolymer films, for example gelatin, agarose, dextrose, and lipid.
Furthermore, it was surprisingly found that it is feasible to produce such biopolymer films also within the range of thickness relevant for the thin layer techniques of from 30 nm to 3 xcexcm to satisfy very high quality standards. Moreover, it was found that certain dyestuffs or photoactivatable groups effect a cross-linking of the biopolymer layer subsequent to a photochemical activation so that their enzymatic decomposition rate considerably slows down compared to unexposed layer ranges.
The layer thicknesses are reproducible within a range of a few 10 nm from solutions with a solids content from 1 to 30% by spin coating which itself is known. Layers applied in such a manner are even in such an extremely thin layer range unexpectedly homogeneous and free of defects. They also resist tempering steps of up to 250xc2x0 C. without any problems and without any signs of degradation during the further process of microstructuring.
The main advantage of such layers from biopolymers, however, consists in their enzymatic degradability which results in a high specificity of degradation which generally takes place under moderate conditions, at ambience, and in solutions exhibiting a pH number preferably from 4 to 9. Basically biopolymers offer the advantage that they provide definite functions for coupling covalently, but also non-covalently further molecules and layers.
Thus, for example, it is feasible to couple to a gelatin layer by way of carboxy-, amino-, and thio-functions but also by way of hydrogen bridge linkages. Furthermore it is feasible without any problems to cross-link biopolymers (for example, by means of glutaric dialdehyde in the presence of a free keto-, amino-, or hydroxyl group), and, hence, to respectively vary the properties of the produced layer.
Thus, for example, a hydrosoluble gelatin changes to a water-insoluble material after a cross-linkage in that molecules are enclosed therein or, alternatively, are bound thereto covalently or non-covalently. Depending on their formation, the proposed thin layers, in the field of application concerned, can be used to various ends.